Chapter Eleven
Sarah is late arriving and Messick has already begun questioning his first witness of the day.
“...and your work has been written up in the Journal of the American Medical Association, the Journal of Forensic Medicine, the Journal...”
Crawley interrupts. “Once again we would like to save the court's time by stipulating that Dr. Johansen is an expert in her field of forensic pathology.”
“Thank you, Mr. Crawley.” Judge Watts actually smiled at Crawley, apparently thankful again that he would save her so much time. She turns to Messick and simply nods for him to continue. Messick flips over a page on his yellow pad and finds the question he was looking for.
“Dr. Johansen, how do you find the cause of a disease?”
“Basically, you're usually looking for something like a bacterium, a fungus, a virus, a parasite, or some other microbe – some other germ – as the causal agent.”
“If you would, please give the jury a quick example of each.”
“Well, the diseases of salmonella and tuberculosis are both caused by bacteria. Of course, there was the polio virus. A fungus causes Valley Fever...do you want more?”
Messick looks at the jury and decides that they’ve understood so far. “No, that’s fine, thank you.” He pauses briefly. “And how can you tell when something is a causal agent for an infectious disease – when it has caused that disease?”
“There are rules. There are criteria any causal agent must meet.”
“What are those rules?”
“They're called ‘Koch's Postulates,’ after Dr. Robert Koch, who was a bacteriologist who lived in the late 1800’s. He came up with the rules, and we in the scientific and medical communities have lived by them ever since.”
“And you're saying that in order to be called the cause of an infectious disease, a bacterium, or a fungus, or a virus must conform to Koch's Postulates?”
“Correct.”
“So what are Koch's Postulates?”
Dr. Johansen rearranges herself in the witness chair, thinking that this might take longer than she had hoped.
“There are four of them. Number One is that the microorganism – the bacteria, fungus, or virus – must be found in every case of the disease and detectable in the infected host at every stage of the disease. Number Two...”
Messick breaks in abruptly. “I'm sorry, let me interrupt.” Then he reconsiders. “Well, actually, maybe you should just give us all four postulates as simply as you can, and then we'll go back and talk about each one in more detail. Go ahead, Dr. Johansen.”
“Number Two is that the causal agent must be able to be isolated from all other microbes and grown independently in a laboratory culture.” She pauses and looks at the jury, wanting to make sure they were listening and she was being understood. It was a pride thing, and a hangover from when she taught in medical school.
“Number Three is that when healthy animals are infected with pathogens from the pure culture, they must come down with the exact same disease. And Number Four is that the microorganism must be re-isolated from the newly diseased animal and must correspond to the original microorganism in pure culture.”
Messick knew there was no way the jury could have followed all that. He didn’t think most people could, especially Postulate Number Four.
“Okay, thank you, Dr. Johansen. So let's go back and take one at a time and make sure we understand. Postulate Number One...”
“Postulate Number One is pretty simple. It requires that something cannot be said to cause a disease unless it can be found in every case of the disease. It makes sense that if you are going to call a bacterium, for example, the cause of tuberculosis, you must be able to find that same bacterium in every case of tuberculosis.”
“And you have to find the polio virus in every case of polio.” Messick thought he could help out a little. “It wouldn't make any sense to have a case diagnosed as polio and not have the polio virus present, right?”
Dr. Johansen nods in agreement. “Right.”
“That makes perfect sense.” At least it did to Messick, and he hopes it did to the jury as well. “Let’s move on to Postulate Number Two.”
“Number Two is more technical. It says that we, as researchers, must be able to find this agent in a diseased body and separate it from any other bacteria or fungi or viruses – in other words, isolate it by itself – and then reproduce it in our laboratories. This proves that the causal agent is alive and active, reproducible, and acting independently from anything else.”
Messick watched the jury the entire time Johansen was speaking, and he didn’t see any signs of their getting lost. That’s good. That’s really good.
“All right. So now that you have this suspect isolated and growing in your laboratory where you can test it, what do you do with it?”
“Well, that’s Koch’s Postulate Number Three, which also makes common sense. It says that if you take this microbe – this germ – and put it into a healthy body, that body must get sick just like the first body.”
“In other words, this microbe must create the same disease when introduced into an otherwise healthy body, which is usually a test animal.”
“That’s correct, Mr. Messick. And if this microbe doesn't make another body sick, it couldn't have caused the original disease, now, could it?”
“No, I agree.”
“And Number Four just completes the cycle and says that when you find the causal agent in the newly diseased animal – the one you've just infected – it must match the original microbe exactly – the one you found in the original body. They've got to be the same in both bodies, in other words.”
Messick is very pleased that they hadn’t blown the jury away with this. It’s not easy for someone who doesn’t work with Koch’s Postulates every day; but with this background laid down, he was on the verge of his first major score. Just a couple more key points….
“Dr. Johansen, to be called the cause of an infectious disease, how many of Koch's Postulates must be met?”
“All four, of course. All four of them.”
“And if an agent – a bacterium, or a fungus, or a virus – fails the test in any one of these four postulates...”
Dr. Johansen didn’t wait for Messick to finish his question. “Then it cannot be the cause of the disease. Period.”
“No exceptions?”
“No. None. If even one of these Postulates is not met, it's back to the drawing board to look for another cause.”
“So if the bacteria that we now know causes tuberculosis had not been found in every case of the disease…”
Dr. Johansen interjects, “It could not have been the cause of tuberculosis.”
“Even just one body, Dr. Johansen?”
“Even just one body, Mr. Messick.”
“And if you injected the virus you thought caused polio into a normal, healthy body, but that body didn’t get polio…”
Dr. Johansen understood now that Messick wanted her to finish his sentences for him. “Same thing. That virus could not have been the cause of polio.”
“Even just one body, Dr. Johansen?”
“Even just one body, Mr. Messick.”
Messick pauses to find exactly the right wording to get the jury to remember the key points of this testimony.
“Dr. Johansen, I realize that as a scientist, all four of Koch’s Postulates are important.”
“Absolutely.”
“But as a layman, it seems to me that I could summarize them by saying that for something to be the cause of an infectious disease, you have to find it in every case of the disease, and it has to cause the disease every time it’s introduced into a healthy body.”
“Well, yes, that is the crux of it.”
Oh, this is going so well. Let’s wrap this up. “Dr. Johansen, is there anything in modern scientific research to suggest that Koch’s Postulates need to be changed, updated, or even ignored?”
“I shoul
d hope not! Without these criteria, how would we decide what caused a disease and what didn't, and therefore how to treat it? Besides, they make perfect sense, don’t they?”
“Yes, they do.” Messick looks directly at the jury. “Yes, they do, Dr. Johansen. Thank you.”
Messick looks across the room at Crawley, sitting at the defense table, as if to ask whether Crawley has changed his mind yet and wants to cross-examine this witness. Crawley turns and begins to confer with a few other members of the defense team. After a couple minutes, Judge Watts gets impatient.
“Mr. Crawley? Do you wish to ask questions of this witness?”
Crawley finishes his whispered conference and stands. “No questions, Your Honor.”
Judge Watts turns back to Messick. “Mr. Messick, you can proceed with your next witness.”
“Thank you, Your Honor. I call Dr. Arnold Peterson.”